Dizziness is a Health Concern. Vestibular Disorders and Rehabilitation. ReZlexes. ReZlex (cont.) Functions of Vestibular System. Dysfunction 2/24/13

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1 Vestibular Disorders and Rehabilitation Week 8: Dr. E Dizziness is a Health Concern From , 35.4% of US adults age 40 y/o and > had vestibular dysfunction. People with a measured vestibular dysfunction who are also symptomatic have a nearly 8x increase in odds of falling. Dizziness is a common symptom affecting about 30% of people > 65 y/o. A majority of individuals > 70 y/o report problems of dizziness and imbalance, and balance- related falls account for more than ½ of the accidental deaths in the elderly. BPPV is the most frequent cause of vertigo in the elderly. ReZlexes Vestibulo- Ocular ReZlex (VOR): compensates for head movement by moving the eyes at a velocity equal to head velocity in the opposite direction. 1:1 ratio. Vestibulo- Spinal ReZlex (VSR): visual and somatosensory cues to maintain balance. Vestibulo- collic rezlex (VCR): acts on the neck to stabilize the head; rezlex produced counters the movement sensed by the otolithic or SCC canals. ReZlex (cont.) Cervico- ocular ReZlex (COR): works with VOR- eye movements driven by neck proprioceptors. Facilitated when the vestibular system is injured. Cervicospinal ReZlex (CSR): changes in limb position driven by neck afferent activity. Supplements the VSR. Cervicocollic ReZlex (CCR): cervical rezlex that stabilizes the head on the body. The extant that is contributed to head stabilization is undertain, but appears to be useful in vertical plane and may be facilitated after labyrinthine loss. Functions of Vestibular System Gaze Stability: VOR compensates for head movements by moving the eyes at a velocity equal to the head velocity in the opposite direction to the head. Postural Stability: VSR assists with visual and somatosensory cues to maintain balance. Sense of Orientation Detection of Linear and Angular Acceleration Other: integration of arousal and conscious awareness of the body via connections with the vestibular cortex, thalamus, and reticular formation. Oscilopsia (VOR dysfxn) Disequilibrium Vertigo and Dizziness Sense of tilt/lateropulsion Imbalance Motion Sensitivity Gait DifZiculties Falls Dysfunction Problems with vision, muscles, concentrations, and memory/attention span Suffer headaches, muscular aches (back/neck) Increased sensitivity to noise and bright lights 1

2 Vestibular System Organization Sensory Input (peripheral)= Afferent Hair cells in the otoliths and semi- circular canals Central Processing= Central Vestibular nuclei in the midbrain Adaptive processor/cerebellum Motor Output (peripheral)= Efferent Eye movements=vor Postural Movements= VSR Sensory System in Postural Control Vestibular: provides CNS with info about movement, speed, and acceleration of head with respect to gravity. Visual: orients us to the environment and provides info about slow movements or static tilt of head with respect to visual Zield. Helps us orient the body in space by using a reference to the objects around us. Somatosensory: provides info about the support surface and what position the body is at all times (positional info). Sensory System in Postural Control Normal/healthy Individuals: the systems work in harmony to provide the most accurate information to the CNS. Sensory reweighing in different contexts When one sensory system abruptly or gradually changes the input to the CNS dizziness and imbalance can occur. Vestibular system serves as a reference for the somatosensory and visual system. Central Processing of the Vestibular System Cerebellum is responsible for the Zine- tuning of the motor outputs (VOR and VSR). Essential role in neural plasticity and adaptation Adjusts for error signals coming from malfunctioning or absent vestibular system Feedforward and Feedback Loops Combines sensory inputs, weighs them according to their relevance and reliability, and provides a resonable estimate of orientation in space. Motor Output of the Vestibular System Gaze stabilization while the head and body are in motion is one of the major functions of the vestibular system 4 oculomotor control systems that keep the fovea on a given target Saccades: voluntary/central control Smooth pursuits: voluntary/ central control Vergence: voluntary/ central control VOR: rezlexive/peripheral vestibular system To stabilize a given target with head movement Vestibular Portion of Labyrinth Semicircular Canals Anterior/Superior Posterior/Inferior Horizontal/Lateral Otoliths Utricle Saccule Blue is Bony Orange is Membranous 2

3 Principles of the Vestibular System Tonic Firing Rate Vestibular nerve and nuclei have a normal resting Ziring rate of cycles/sec Baseline Ziring rate present without head movement Tonic Ziring rate is equal in both sides (if not, sense of motion) Velocity Storage System Normal VOR can deliver high standards of performance for brief head motions (Ziring rate decays to 32% in 7 sec=time constant) Used as a repository for info about head velocity Keeps vestibular related responses going after vestibular afferent info decays. Principles of the Vestibular System Push- Pull Relationship Excitation and inhibition (always together) Actions that stimulate one inhibit the other Inhibitory Cut- off Beyond a certain velocity, excitatory stimuli causes a greater response than inhibitory stimuli Ewald s 2 nd Law: depolarization (excitation) of the cupula within the inner ear does not saturate, whereas hyperpolarization (inhibition) does. The system can be excited more than it can be inhibited. Semi- Circular Canals Detect Angular Acceleration Aligned at right angles to each other Horizontal slopes 30 deg down and back Work in pairs/coplanar R anterior/l posterior L anterior/r posterior R/L Horizontal Both ends attach to the utricle One end widens into a bulb- like area called the ampulla/crista ampullaris The non- ampulla ends of the anterior and posterior canal fuse to form the common crus Otoliths Detect Linear Acceleration Including gravity (static tilt of head) Utricle: horizontal Saccule: vertical Functional unit is Macula Also work in paires Cupula Impermeable diaphragm like structure connecting sensory hair cells at the crest of the ampulla to the roof of the ampulla. Same specizic gravity as the surrounding endolymph, so its presence does not make the SCC s sensitive to the static pull of gravity. Inertia causes the endolymph Zluid to be pushed against the cupula causing an angular displacement of the hair cells. Membranous labyrinth moves with head motion, the endolymph does not, causing a relative endolymph motion opposite of the head motion. Sensory End Organ Hair Cells Embedded inside each of the 3 cupula and in the macula of the otolith organs Composed of ciliary bundles When they are dezlected toward the largest hair, the hair cell is depolarized which increases the Ziring rate/ excitation of the vestibular nerve Zibers to the brainstem When the hairs are dezlected away from the largest hair, they are hyperpolarized which causes a decrease in Ziring rate/inhibition of the corresponding vestibular nerve. 3

4 Otolithic Membrane Saccule and Utricle Hair cells within the macula project up into membrane Gelatinous membrane embedded with otoconia Increases the specizic gravity of the membrane compared to the Zluid surrounding it, causing the otoliths to be responsive to the static pull of gravity. Central region is called striola. Peripheral Vestibular Causes Benign Paraoxysmal Positional Vertigo (BPPV) Vestibular Neuritis Acoustic Neuroma Bilateral Vestibular Loss Meniere s Disease Fistulas Temporal Bone Fracture Post- traumatic vertigo Labyrinthine Concussion BPPV Caused by mechanical displacement of otoconia from the otolithic membrane of the utricle into one of the SCC s Idiopathic or Traumatic Most Common Cause of Vertigo Signs/Symptoms Sudden onset True vertigo/spinning Sensations Latency of 1-5 seconds Lasts only seconds Induced by changes in head position Visible nystagmus Reversal of nystagmus direction on returning to upright Response diminishes with repetition of maneuver (fatigability) Test: Dix- Hallpike or Roll Test Vestibular Neuritis Sudden Onset with vertigo and nausea lasting ~ 2 days 2 nd most common cause of vertigo Residual head motion provoked dizziness and imbalance Acute Phase: spontaneous horizontal nystagmus beating toward non- involved ear (always beats toward the most active side) Primary cause: viral Unilateral loss (UVL) PT is very effective Tests: + head thrust, DVA, head shaking nystagmus, vestibular funciton testing Meniere s Disease Endolymphatic hydrops: malabsorption of the endolymph in the endolymphatic duct and sac. Symptoms persists from minutes to 24 hours. Meniere s Triad Fluctuating unilateral hearing loss Episodic vertigo Tinnitus Requires medical diagnosis/testing to conzirm Not appropriate for PT in active state Control with diet, medication, and external devices. Acoustic Neuroma Tumor originates in the Schwann cells lining the axons of the VIII cranial nerve. Typically benign (MRI/CT to conzirm) Surgical Management PT following surgery to promote compensation for vestibular loss Signs/Symptoms Gradual Hearing Loss Tinnitus Imbalance Positive Hyperventilation Testing 4

5 Bilateral Vestibular Loss Acute Onset: ototoxicity typically from Gentamycin or Chemotherapy (Cisplatin) Gradual Onset: common in elderly with degeneration of hair cells or subsequent UVL s. Signs and Symptoms Severe Imbalance Will have NO dizziness/vertigo with complete loss Unable to walk or balance in the dark + Head Thrust Bilaterally Fistulas Perilymph Fistula is an abnormal connection between the air- Zilled middle ear and the Zluid Zilled inner ear usually at the round or oval window. Superior Canal Dehiscence: caused by thinning or complete absence of the part of the temporal bone overlying the superior semicircular canal. Cholesteatoma: abnormal growth that invades the mastoid air spaces and can erode into the horizontal SCC causing body Zistula damage. In all cases, vestibular and auditory signs/symptoms provoked by external stimuli such as sound (Tulio s Phenomenon), change of pressure or vibration. Fluctuates with pressure changes Medical: avoid strain, sneeze, cough, or head- hanging postions; surgery Other Vestibular Disorders Temporal Bone Skull Fracture Essentially the patient ends up with a complete loss of equilibrium sense on one side as well as hearing Often associated with TBI Post- traumatic Vertigo Tends to follow head trauma with similar symptoms to BPPV & UVL. Hemorrhage into the labyrinth Prognosis is good with symptoms gradually resolving within weeks to months Vast majority of patients respond to vestibular rehabilitation Labyrinthine Concussion: manifests with ataxia, hearing loss, and imbalance; Bilateral BPPV Most common vestibular injury due to TBI Central Vestibular Disorder Vascular: Wallenberg s Syndrome, Head injury, cerebellar infarct, Vestibular Nuclei of midbrain. Demyelinating Disease/MS Post- Concussive Syndrome Congenital: Arnold- Chiari Degenerative Cerebellar Disease: abnormal ocular pursuit, irregular saccades, gaze and end point nystagmus, ataxia. Gradual Decline. Concussion Dizziness is a frequent symptom of concussion and has been reported to occur in 23-81% of cases in the Zirst days after injury. Poor balance, postural instability Oculomotor signs, impaired smooth pursuit, vertigo, and perception of tilt VRT had a signizicant treatment effect for all self- report and performance measures. Vestibular Dysfunction Acoustic Neuroma BPPV Labyrinthitis/Neuritis Meniere s Disease Temporal Bone Fracture Cnetral Vestibular region Ototoxicity/BVL Perilymph Fistula Superior Canal Dehiscence Labyrinthine Concussion Hemorrhage within vestibular system 5

6 Multi- factorial Hyperventilation Other Causes Peripheral Neuropathies Stress/tension/fatigue/depression Medications Blood sugars Cardiac Systemic Non- Otogenic causes of Dizziness Aneurysm Arrhythmia Atherosclerosis Defective heart valve Dehydration Degenerative arthritis Embolism Heart Attack Hyperventilation Medications Orthostatic Hypotension Osteoarthritis Peripheral Neuropathies Stress/tension/fatigue Tumor in brain stem Visual disturbances Mal de Debarquement Vertebral Basilar InsufZiciency Cervicogenic Anxiety Disorder Chronic Subjective Dizziness/Visual Vertigo Vestibular Rehabilitation Designed to provide small, controlled, and repeated movements that provoke dizziness and/or unsteadiness in order to: Desensitize the balance system to the movement Enhance the Zine- tuning involved in long- term compensation Three compensation techniques Adaptation: ability to make long term changes in the neuronal response to head movement with the goal of decreasing retinal slip and increasing the gain of the remaining vestibular system Substitution: BVL, alternative strategies to overcome loss Habituation: long- term reduction of a response to a noxious stimulus= more you move, the better you feel. 6